1. Field of the Invention
The present invention relates to laser systems for medical treatments and in particular, for laser surgical procedures. More particularly, it relates to optical fiber systems and methods used for the treatment of various surgical procedures, including benign prostatic hyperplasia.
2. Information Disclosure Statement
Many important medical conditions suffered by many patients require treatments which consist in removing abnormal soft tissue from the body. Undesired tissue may include tumors and atheromatous plaques, excess fat in aesthetic treatments, or portions of prostate tissue. In urology, for example prostate disorders such as cancer or benign enlarged prostate (BPH) require this tissue to be partially or totally removed.
Tissue removal can be performed by means of different methods. Independently of the method used, the main objective of this kind of treatment is the removal of the whole undesired tissue while preventing from damage of surrounding tissue. In recent years, laser energy has been used in order to accomplish this aim.
Based on laser energy applied on tissue, numerous approaches have been proposed. Laser techniques are usually preferred due to its special capacity of delivering high amounts of power on reduced areas, thus improving treatment precision and accuracy and diminishing undesired effects on surrounding tissue.
Prostate cancer affects over 232,000 men in the US every year. It is a malignant tumor growth that consists of cells from the prostate gland. The tumor usually grows slowly and remains confined to the gland for many years. During this time, the tumor produces little or no symptoms or outward signs (abnormalities on physical examination). As the cancer advances, however, it can spread beyond the prostate into the surrounding tissues. The cancer can also metastasize throughout other areas of the body, such as the bones, lungs, and liver. When detected before metastasis, laser surgery employing side-firing fibers is currently a preferred treatment among surgeons and patients. It causes little blood loss and allows for a shorter recovery time.
Benign prostatic hyperplasia (BPH) or “enlarged prostate” refers to the noncancerous (benign) growth of the prostate gland. While BPH is the most common prostate problem in men over 50 years of age, benign growth of the prostate begins with microscopic nodules around 25 years of age but rarely produces symptoms before a man reaches 40. It is estimated that 6.3 million men in the United States have BPH and the disease is responsible for 6.4 million doctor visits and more than 400,000 hospitalizations per year.
The exact cause of BPH is unknown but it is generally thought to involve hormonal changes associated with the aging process. Testosterone likely has a role in BPH as it is continually produced throughout a man's lifetime and is a precursor to dihydrotestosterone (DHT) which induces rapid growth of the prostate gland during puberty and early adulthood. When fully developed, the prostate gland is approximately the size of a walnut and remains at this size until a man reaches his mid-forties. At this point the prostate begins a second period of growth which for many men often leads to BPH later in life.
In contrast to the overall enlargement of the gland during early adulthood, benign prostate growth occurs only in the central area of the gland called the transition zone, which wraps around the urethra. As this area of the prostate grows, the gland presses against the urethra, leading to difficult or painful urination. Eventually, the bladder itself weakens and loses the ability to empty by itself.
Obstructive symptoms of BPH such as intermittent flow or hesitancy before urinating can severely reduce the volume of urine being eliminated from the body. If left untreated, acute urine retention can lead to other serious complications such as bladder stones, urinary tract infections, incontinence, and, in rare cases, bladder and kidney damage. These complications are more prevalent in older men who are also taking anti-arrhythmic drugs or anti-hypertensive (non-diuretic) medications. In addition to the physical problems associated with BPH, many men also experience anxiety and a reduced quality of life.
Mild symptoms of BPH are most often treated with medication such as alpha-blockers and anti-androgens. Men suffering with moderate to severe BPH symptoms typically must undergo surgery. There are a number of different laser techniques in which light is used to eliminate excess prostate tissue either by ablation (vaporization), thermal coagulation or a combination of these mechanisms. The observed clinical effects are due to the absorption of light (by the target tissue itself and/or surrounding fluids) and subsequent heat transfer, the extent of which largely depends on the power and wavelength of the laser beam.
Many types of laser surgeries are able to provide a near-immediate improvement in the urinary stream. Laser surgery for BPH can have other potential advantages such as reduced blood loss as well as shorter treatment times, faster patient recovery, and a lower risk of post-treatment incontinence, depending on the wavelength and technique used. However, many patients still require catheterization for 1-2 weeks post-treatment after undergoing some forms of laser surgery.
An important factor determining the success of laser surgery in urology is the accuracy with which the surgeon is able to eliminate undesired prostate tissue to achieve adequate tissue ablation without damaging surrounding healthy tissue. Accuracy is defined not only in mechanical terms but also in confinement of the treatment beam, whether or not significant decanting of the tissue occurs before ablation, and other concerns. To achieve some success, inventors have worked over the years on developing optical fiber configurations that can improve efficiency, accuracy and thus safety of the procedure. Fibers must also be able to withstand the high laser energy emitted by new laser source technologies. In BPH treatment, laser beams oriented at a certain angle with respect to the main fiber axis are preferred, for more effective tissue ablation. U.S. Pat. No. 5,292,320 by Brown et al. discloses a side firing output end having multiple side fire surfaces within the fiber core. The fiber core has a plurality of grooves as well as a slanted end surface for reflecting laser energy in a lateral manner. This approach helped efficiency but was a complex structure to make, and if care was not exercised working tip could be fragile. Furthermore since the core is glued into the end cap, under high power laser operations, for example, 50 W or greater, this output end often fails.
U.S. Pat. No. 5,509,917 by Cecchetti et al. disclose a lateral beaming laser tip having a transparent quartz cap about the output end of the optical fiber therein. The cap is shown having various focusing means for the laser radiation reflected off of the slanted end surface of the optical core. This laser tip is generally complex to manufacture and connection to the underlying fiber also can be variable and difficult to repeatedly produce.
In U.S. Pat. No. 5,366,456, Rink et al. depict a laser cutting scalpel wherein the transmitted radiation is delivered at an angle to the incident radiation source and tool. The device has a firing tip which has an insert with a highly polished minor surface lying at a specific angle with respect to central longitudinal axis of the optical fiber. Thus, impinging laser radiation is reflected to the side and delivered at approximately a right angle to the fiber. The firing tip can be mounted on the tip of a cannula, the entire apparatus being rotatable about the central axis of the fiber. Brekke et al. in U.S. Patent Publication 2006/0285798 claim a bent side-firing laser for redirecting light laterally relative to an axis of the apparatus. Various aspects of the construction and use of the fiber are complex and potentially difficult to reproduce uniformly from case to case. In U.S. Pat. No. 5,428,699, Pon discloses an optical fiber for laterally directing a laser beam similar to Brown and Cecchetti where thick claddings are used to decrease scattered electromagnetic radiation from the internal reflecting structure and thereby improving the efficiency of the laterally directing probe. All three previously mentioned patents claim that radiation beam is emitted laterally with respect to probe's main axis, in a non-contact mode. They improve some features over the prior art, though many of the shortfalls of laterally firing systems remain, including how to maintain uniform non-contact and keep from ‘fouling’ of the active emitting surface.
U.S. Pat. No. 5,553,177 by Herring et al. depicts a lightguiding device that consists of a section of a lightguiding material which has been bent at an angle of about 90 degrees relative to the axis of light transmission with a small bend radius. The output is radiated asymmetrically from the fiber axis. The bent section is treated to obtain a homogenous refractive index in the lightguide's core. Problems here are difficult to form small sharp angle, often a fragile structure, especially, in smaller dimensioned fibers. In U.S. Pat. No. 5,416,878, Bruce depicts a side firing laser fiber in which the output end terminates in a flat face having an accurate edge around its circumference. It has a bend close to the emitting face of the fiber which results in a laser beam directed at a certain angle from the longitudinal axis of the main body of the optical fiber. Here, the difficulty of rotational movements by the surgeon represents a main drawback. Also while some improvements in forming shallower bend, the tip is still somewhat subject to accidental breakage. Another disadvantage, is that both inventions present a flat surface end, limiting light focusing characteristics of fiber, which becomes important, for example, if steam bubbles appear in front of fiber, a common situation at high powers. Furthermore, flat surface may damage or perforate non target tissue as well.
U.S. Pat. No. 6,699,239 by Stiller et al. discloses a laser instrument for vaporization of biological tissue and stabilization of the application cap during tissue removal. The laser instrument includes an optical waveguide with a light guide portion that emits light and an application cap coupled to the optical waveguide that transmits light. The laser instrument can be inserted into an endoscope and extended or retracted to position the application cap for vaporization and removal of biological tissue. This invention presents some characteristics which represent important drawbacks. For instance, fiber tip is fused with receiving sleeve, but optical waveguide is joined mechanically to the application guide by means of bonding between the sheathing and the receiving sleeve. This renders device potentially vulnerable to deterioration when high temperatures are present, and if high energy is applied, end cap may become detached while inside body, representing a hazard for the patient and a complication for the surgeon. Furthermore, end cap is composed of two parts, mainly a fiber positioned within a curved glass end. Therefore, in a liquid medium such as inside the urethra, laser radiation is transmitted through the material of end cap, that is, from the outer area of the curved part of the probe and emerging from multiple sites. This may represent a difficulty for the surgeon as it is difficult to point radiation in a precise direction so healthy tissue will also be damaged. This fact also renders a reduction in power density. Finally, due to optical coupling between fiber and cap, light losses and reflection could diminish efficiency of treatment.
As can be seen from previously mentioned patents, prior inventions present several drawbacks, such as those related to difficulty of maneuvering, focusing possibilities and energy limitations. Prior art is also limited in that treatment is not always as effective as desired as they are time consuming. As newer technologies arise, physicians strive for achieving shorter procedure times to satisfy their patients, and at the same time to be able to treat more patients daily.
There is thus a need for a laser treatment system that improves on the state of the art, providing a better, more robust, fiber tool to enhance speed of removal, ease of handling/working, while maintaining the benefits of laser cutting. The present invention addresses these needs.